n. A half-sphere; one half of a sphere or globe formed by a plane passing through the center. Specificallyn. Half of the terrestrial globe; also, half of the celestial globe, or of the surface of the heavens.n. A map or projection of half of the terrestrial or the celestial sphere.n. In anatomy, either of the two large convex and convoluted masses, one on each side, which together with the fornix, corpus callosum, thalamencephalon, mesencephalon, and olfactory lobes make up the cerebrum. See brain, cerebrum, and cerebral.